On the third anniversary of the 25-year-old Bangor woman's disappearance, Detective Chief Inspector Sean Wright said it is not too late for those who know what happened to Lisa to hand over that information.

"The key to solving this case, and bringing closure to Lisa's family, is held by a very small group of people. These people could make a real difference to Lisa's family at this difficult time - it is not too late," he said.

Mr Wright added: "They know who they are and detectives will continue to try and glean information from the community as part of ongoing efforts to find Lisa and lead police to whoever killed her.

"We appreciate that the third anniversary of Lisa's disappearance is a very difficult and emotional time for her family.

"Our work will continue and those responsible for Lisa's death should take no comfort from the fact that, thus far, they have not been made amenable."

Lisa went missing in the early hours of February 28, 2005, from a caravan at Ballyhalbert.

Police believe her body was moved out to sea some months after she was murdered and have appealed to people in the sailing community to come forward with any information they believe may be useful.

For the past three years the heartbroken Dorrian family have campaigned tirelessly for Lisa's body to be returned to them.

Her sister Joanne has said the family, who have issued a £30,000 reward for information, are no longer concerned about justice, they just want to find her body.

"We have been living with the nightmare of not knowing where Lisa is for the last three years and the pain is just getting worse as each day passes.

"If we were presented with the choice of securing justice for my sister's killing or having her home then we would chose getting Lisa back every time," she has said.

South Down MP Lady Sylvia Hermon said the past three years have been " absolutely harrowing" for Lisa's devoted family.

"Three years on from Lisa's disappearance and still no body, no funeral, no grave," she said.

"It's been absolutely harrowing for her devoted family, who have shown remarkable dignity and fortitude throughout what can only be described as a living nightmare. They have had to come through three Christmases without her, birthdays without her, Mother's and Father's Days without her."

Lady Sylvia added: "Their longing to have her home remains undiminished by the passage of time. Someone out there must know what happened to Lisa Dorrian and must know where her body was left.

"To them I would say it's never too late to do the right thing. Any information, however small, may nevertheless lead to her recovery. Step forward now, give the police that information to put an end to the heartache and suffering of the Dorrian family, who still love Lisa very much and always will."

Anyone with information about Lisa's disappearance, her murder or where her body rests, has been asked to contact detectives on 0845 600 8000 or Crimestoppers anonymously on 0800 555 111.

Alternatively, people can send information anonymously to Lisa's family via the website www.lisadorrian.co.uk.